Chemically Stable and High Acid Recovery Anion Exchange Membrane

Herein we are reporting a base-catalysed carbanion formation of N-methyl-4-piperidone (NMPi) and thermoset anion exchange membrane thereof. N-methyl-4-piperidone (NMPi) was reacted with formaldehyde in presence of sodium hydroxide to obtain NMPi-formaldehyde based prepolymer. An anion exchange membrane (AEM) was obtained by grafting prepolymer on to polyvinyl alcohol (PVA) by thermal annealing followed by quaternization. By varying the NMPi/PVA ratio, four AEMs namely M1-M4 was synthesized. Detailed physicochemical, microscopic, thermal and dimensional stability studies were performed to assess their applicability. AEMs were explored for acid recovery from hydrochloric acid (HCl), sulphuric acid (H2SO4), acetic acid (CH3COOH), simulated feed (2 M HCl containing 6% FeSO4) and effluent from a local bentonite mine (acid concentration ~8 M) by diffusion dialysis. Proton dialysis coefficient (UH+) of 22 x 10-3 m h-1, Fe2+ dialysis coefficient (UFe 2+) of 1.94 x 10-5 m h-1 and separation factor (S) of 112 units for best performing membrane was obtained for simulated feed. Acid recovery of 80% was achieved in 50 h from effluent obtained from local bentonite mine by changing the permeate side thrice at diffusion equilibrium; encouraging its best applicability and stability in highly acidic environment.